The rapid development of communications technologies not only brings convenience to people's lives, but also puts forward higher technical requirements for people. With respect to a communication device, a frequency characteristic is a very important performance index. Because the communication device is affected by a material thermal expansion characteristic, the frequency characteristic of the communication device alters with a temperature change.
In particular, the temperature has an extraordinarily prominent influence on a filtering characteristic of a narrowband cavity filter. Generally, a change of the temperature brings about a frequency band drift to a radio frequency index, commonly known as “temperature drift,” which may lead to reduction in functions of a radio frequency system. In addition, as the mobile communications evolve to a high frequency band, the temperature drift phenomenon becomes increasingly serious. For example, with respect to a cavity filter in a worldwide interoperability for microwave access (WiMAX) 2.6 gigahertz (GHz) or 3.5 GHz standard, the frequency band drift phenomenon brought about by the change of temperature to the cavity filter has been very serious.
Therefore, some communication devices manufactured by using conventional materials can not satisfy requirements on frequency characteristics with the rapid development of the communications technologies, which has become one of the factors that impedes the development of the communications technologies.